The objective of this test to assert text returned from a SelectAll call on WebContent is same as text from WebLocalFrame::ContentAsText.

This is a patch that refers to the following CL
https://codereview.chromium.org/342143004/

Review URL: https://codereview.chromium.org/464613003

git-svn-id: svn://svn.chromium.org/blink/trunk@180208 bbb929c8-8fbe-4397-9dbb-9b2b20218538